CN1706013A - Highly insulated inductive data couplers - Google Patents

Abstract

There is provided an inductive coupler for coupling signal to a power line. The inductive coupler includes a magnetic core for placement about the power line, a coil wound about a portion of the magnetic core, and a semiconducting coating that encapsulates the core and contacts the power line. The signal is coupled to the coil.

Description

Highly Insulated Inductive Data Couplers

technical field

The present invention relates to power line communications and, more particularly, to a data coupler that is insulated in a manner that minimizes voltage breakdown.

Background technique

Inductive couplers for power line communications couple data signals between a power line and a communication device such as a modem. Inductive couplers may suffer insulation breakdown or partial discharge at unreasonably low line voltages. Breakdown or partial discharge typically occurs at locations within the coupler where the electric field is concentrated in the insulating material or creates a very high intensity electric field through the air.

Figure 1 shows a cross-section of a prior art inductive coupler. The power line 800 (e.g. the phase line) serves as the primary winding of the inductive coupler and thus passes through the bore of the magnetic circuit with the core configured with an upper core section comprising core 805 and comprising core 810 The lower core portion, and air gaps 830 and 835. The secondary winding 820 surrounded by insulating material 825 also passes through this hole. The power line 800 is in contact with the core 805 at contact point 855 and the secondary winding 820 is grounded. Cores 805 and 810 are made of magnetic core material. The electric field inside cores 805 and 810 is determined by the conductivity and permittivity of the core material.

With the power line 800 bare, the full phase voltage is applied to the coupler, specifically between the contact point 855 and the secondary winding 820 .

Referring to FIG. 2 , which shows a situation where a power line 800 is covered with insulation, the power line 800 is shown having insulation 860 in contact with the core 805 at a contact point 865 . A capacitive voltage divider is formed between (a) the capacitor formed between the power line 800 , the insulating material 860 , and the core 805 and (b) the capacitance between the contact point 865 and the secondary winding 820 . Therefore, the voltage stress between contact point 865 and ground is less than the full phase voltage.

On the plane where the secondary winding 820 leaves the core 810, the core 810 presents a sharp corner. In general, there may be two locations where ionization and voltage breakdown can easily occur: (1) the air path 840 between the power line 800 and the insulating material 825, and (2) the corner of the core 810 and the secondary winding 820 leaving The area between the outlets of the core 810 .

The air path 840 is prone to ionization and voltage breakdown, as explained below. The insulating material 825 is likely to be constructed of plastic or other material with a dielectric constant of 2.5 to 3.5. The capacitive voltage division of the voltage difference between the power line 800 and the secondary winding 820 will be such that the vast majority of the voltage difference is on the air path 840 and relatively very little is through the insulating path 850 . Air is less insulating than plastic or other insulating materials, so as the voltage on power line 800 increases, breakdown is likely to occur on path 840 .

FIG. 3 shows a horizontal cross-section along the secondary winding 820 (eg, as shown in FIG. 1 ). The lower core portion shown is made up of a plurality of cores (ie, cores 810, 811, 812, and 813). Secondary winding 820 passes through cores 810 , 811 , 812 and 813 . Regions 1000, 1005, 1010, and 1015 represent regions where electric fields are concentrated and may cause initial insulation breakdown while the voltage on power line 800 is still well below the desired voltage.

Contents of the invention

The present invention relates to a data coupler that is insulated in such a way as to minimize voltage breakdown. One embodiment of the invention is an inductive coupler for coupling a signal to a power line. The inductive coupler includes a magnetic core arranged around a power line, a coil wound around a part of the magnetic core, and a semiconductor cladding that seals the magnetic core and is in contact with the power line. A signal is coupled to the coil.

Another embodiment of an inductive coupler for coupling a signal to a power line includes a magnetic core disposed around the power line, and a coil wound around a portion of the magnetic core. The coil includes a coaxial cable, the outer conductor of which has a power line potential, and the cable includes an end with a stress cone.

Description of drawings

Figure 1 shows a cross-section perpendicular to the power line of an inductive coupler of the prior art;

Fig. 2 shows the cross section of the inductive coupler of another embodiment of prior art;

Figure 3 shows a horizontal cross-section along the secondary winding of an inductive coupler such as that shown in Figure 1;

Figure 4 is a cross-section perpendicular to the power lines of a highly insulated inductive data coupler;

Figure 5 shows a horizontal cross-section along the lower magnetic core portion of a highly insulated inductive data coupler such as that shown in Figure 4;

Figure 6 is a vertical cross-section of a structure employing an inductive coupler with a semiconductor cladding;

Figure 7 is a cross-section of a high voltage inductive data coupler incorporating cables as secondary windings.

Detailed ways

A highly insulated inductive data coupler according to the present invention virtually eliminates high electric fields through the air path and confines these high electric fields to locations filled with dielectric material. All energized bodies use rounded geometries to eliminate any pointy features that could generate high local electric fields. Likewise, placing the upper and lower core sections within a single common equipotential envelope makes the coupler independent of the dielectric properties of the core and eliminates in-core and upper and lower core sections. Electric field between core parts.

Figure 4 is a cross-section of a highly insulated inductive data coupler according to the present invention. The coupler includes a magnetic core arranged around the power line 800 . The core is configured with an upper core portion including core portion 805 and a lower core portion including core portion 810 . Designation of core parts as "upper" and "lower" merely indicates their respective positions in the drawings of the present disclosure, and such designations are not necessary to describe the actual physical positional relationship of these core parts. The secondary winding 820 is connected to a communication device (not shown), such as a modem, so that the coupler enables coupling of data signals between the power line 800 and the communication device.

Each of core 805 and core 810 is sealed into a boot or cladding 900 and 905 made of a semiconductor material. Suitable semiconducting materials are eg plastic or rubber impregnated with graphite or corundum to provide the desired bulk resistivity. Electrical contact 910 is formed between cladding layer 900 and cladding layer 905 . Therefore, the cores 805 and 810 and the claddings 900 and 905 become a single substantially equipotential body.

The surface 915 of the insulating material 825 is covered with a semiconductor coating 945 which overlaps the coating 905 and is in electrical contact with the coating 905 . The potential of the coating 945 is thus substantially equal to the surface potential of the electric field line 800 , which eliminates or greatly reduces the voltage across the air path 940 . This allows an inductive coupler comprising secondary winding 820 and cores 805 and 810 and employing power line 800 as the primary winding to be safely used at higher primary voltages than an inductive coupler without semiconductor cladding 945 .

FIG. 5 shows a horizontal cross-section along the lower magnetic core portion of a highly insulated inductive data coupler such as that shown in FIG. 4 . The lower core portion is sequentially arranged with a plurality of core portions, namely core portions 810 , 811 , 812 and 813 . When compared to the inductive data coupler of FIG. 3, the electric field concentration of the inductive data coupler of FIG. 5 is reduced in region 1105 at the exit of the secondary winding 820 from the core 813 (compared to region 1000). . The cladding 905 is configured with a circular profile 1100 that provides a circular extension on the side of the core 813 . Rounding the shape of the excited body (eg, core 813 ) reduces the maximum electric field in region 1105 for a given voltage carried by power line 800 ( FIG. 1 ). Conversely, for a given insulating material 825 (FIG. 1) having a maximum voltage breakdown rating, the voltage applied across the power line 800 can be increased compared to what would be tolerated if a sharp corner were present.

The secondary winding 820 shown in FIG. 5 passes through the core once. In practice, the secondary winding 820 may be configured as a coil wound around a portion of the magnetic core.

In this way, an inductive coupler for coupling a signal to a power line is provided. The inductive coupler includes: (a) a magnetic core disposed around a power line; (b) a coil wound around a portion of the magnetic core, wherein a signal is coupled to the coil; and (c) a semiconductor cladding that seals the magnetic core and contact with power lines. The magnetic core has a longitudinal end, whereby the inductive coupler also includes a circular semiconductor body covering the longitudinal end and in electrical contact with said semiconductor cladding. The coil has wires leading from the magnetic core, so the inductive coupler also includes a semiconducting layer on the ends for reducing electrical stress between the lines of force and the surface of the insulating material covering the coil.

Fig. 6 is a vertical sectional view of a structure using an inductive coupler with a semiconductor cladding. The air path 1200 between the power line 800 and the surface 1210 of the insulating layer 1225 surrounding the grounded secondary winding 1220 is easily ionized and broken down. The potential difference between the power line 800 and the secondary winding 1220 is capacitively divided between the air path 1200 and the insulating layer 1225 . The potential difference over the air path 1200 has a larger proportion than the potential difference over the insulating layer 1225 , but the air path 1200 is a poorer insulator.

To mitigate this, techniques similar to those used in stress cones are employed. Stress cones are used at the termination of two conductor cables and provide a gradually decreasing potential to reduce electric field concentrations that can cause insulation breakdown. This situation is shown in the right half of FIG. 6 . The semiconductor layer 1230 embedded in the insulating layer 1225 is sandwiched between the secondary winding 1220 and the surface 1215 of the insulating layer 1225 and is connected to the cladding 905 of the cores 805 and 810 . The semiconductor layer 1230 includes a combination of series resistance and parasitic capacitance that causes the potential to decrease with increasing distance from the longitudinal ends of the semiconductor core cladding 905 to avoid any transitions at the distal edges of the semiconductor layer 1230. electrical stress concentration. Thus, the semiconductor layer 1230 raises the potential of the surface 1215 close to the primary potential of the power line 800, greatly reducing the potential difference across the air path 125, and preventing breakdown at the unacceptably low primary potential of the power line 800.

The secondary winding 1220 shown in Figure 6 passes through the core once. In practice, the secondary winding 1220 may be configured as a coil wound around a portion of the magnetic core.

Large potential differences on the air path and points of high electrical stress can be eliminated by a combination of techniques. As described above in connection with Figures 4 and 5, in one technique, the cores are covered by a semiconductor layer. For another technique, a length of high voltage cable is used or specially molded for the coupler. The cable has an outer semiconducting layer which is excited by conductive or capacitive contact with the covering magnetic core. The cable has a grounded center conductor. At both ends of the secondary winding, stress cones provide the termination of the cable. If the secondary winding is embedded in insulating material, an indoor stress cone without a shed can be used. Otherwise, a skirted outdoor stress cone can be used to increase the leakage path.

FIG. 7 is a cross-section of a high voltage inductive data coupler 1345 according to another embodiment of the present invention. Coupler 1345 uses a high voltage cable as the secondary winding.

The electric line 800 passes through a core 805 which is covered by a semiconductor layer 900 . The secondary winding 1300 , ie the inner conductor of the secondary cable 1305 , is grounded via a choke, not shown, and via the core 810 , which is sealed in the semiconducting layer 905 . The secondary cable 1305 is covered with a semiconducting layer 1310 which is connected to the semiconducting part 1315 of the stress cone 1320 . The entire lower part of the coupler 1345 is sealed in the insulator 1325 and the coupler 1345 is provided with a skirt 1330 for providing a long leakage path between the power line 800 and the grounded secondary winding 1300 .

Functionally, the electric line 800 or its thin insulating material is in contact with the semiconductor layer 900 and brings the potential of the semiconductor layer 900 close to that of the electric line 800 . The terms "gap" and "air gap" are used to denote a non-magnetic spacer or non-magnetic region between parts of the magnetic core to increase current handling capability and maximum magnetomotive force before saturation. The semiconductor layer 900 contacts the semiconductor layer 905 at a gap 1350 between each core 805 and 810 , bringing the semiconductor layer 905 close to the potential of the electric field line 800 . The secondary cable 1305 has a semiconducting layer 1310 in direct contact with the semiconducting layer 905 so that the semiconducting layer 1310 is also brought to an electrical potential close to that of the power line 800 .

At each end of the secondary cable 1305, stress cones 1320 terminate the secondary cable 1305, allowing the secondary winding 1300 to exit the coupler 1345 without undue localized electrical stress. Due to the lower energized semiconductor layer 1310, the surface potential of the coupler 1345 is close to the potential of the power line 800, so the air path 1340 does not bridge high potentials.

The secondary cable 1305 shown in Figure 7 passes through the core once. In practice, the secondary cable 1305 may be configured as a coil wrapped around a portion of the magnetic core.

Accordingly, another embodiment of an inductive coupler for coupling a signal to a power line is provided. The inductive coupler includes (a) a magnetic core disposed around a power line; (b) a coil wound around a portion of the magnetic core, wherein a signal is coupled to the coil; and (c) a semiconductor cladding that seals the magnetic core and contact with power lines. Furthermore, the coil has a length of high-voltage cable covered with a semiconducting material that is in conductive or capacitive contact with the semiconducting coating, and the inductive coupler also includes a stress cone at the end of the coil.

It should be understood that various substitutions, combinations and modifications of the teachings herein can be made by those of ordinary skill in the art. The present invention is intended to embrace all such alterations, changes and modifications that come within the scope of the appended claims.

Claims (7)

1, a kind of inductive coupler that is used to couple a signal to power line comprises:

The magnetic core that around described power line, is provided with;

Twine the coil of the part of described magnetic core, wherein said signal is coupled to described coil; And

The semiconductor coating, it seals described magnetic core and contacts with described power line.

2, according to the inductive coupler of claim 1,

Wherein said magnetic core has vertical end, and

Wherein said inductive coupler also comprises circular semiconductor body, and described circular semiconductor body has covered described vertical end and electrically contacted with described semiconductor coating.

3, according to the inductive coupler of claim 1,

Wherein said magnetic core has the rounded longitudinal end, and

Wherein said semiconductor coating has covered described rounded longitudinal end.

4, according to the inductive coupler of claim 1,

Wherein said coil has the lead of drawing from described magnetic core,

Wherein said lead is coated with insulation material layer, and

Wherein said inductive coupler also is included in the semiconductor layer on the described insulation material layer.

5, according to the inductive coupler of claim 1,

Wherein said coil has the lead of drawing from described magnetic core, and

Wherein said inductive coupler also is included in the semiconductor layer on the described lead.

6, according to the inductive coupler of claim 1,

Wherein said coil has one section high-tension cable that is coated with semi-conducting material, and described semi-conducting material conducts electricity with described semiconductor coating or capacitive character contacts, and

Wherein said inductive coupler also is included in the stress cone of described coil end.

7, a kind of inductive coupler that is used to couple a signal to power line comprises:

Be used for magnetic core in described power line arranged around; And

Twine the coil of the part of described magnetic core,

Wherein said coil comprises coaxial cable, and the outer conductor of coaxial cable has power line potential, and

Wherein said cable comprises the end with stress cone.

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